Hot-air furnace



Oct. 3l, 1950 F, H, KLUG 2,527,937

HOT-AIR FURNACE Filed Aug. 1o,v 1948 2 Smeets-sheet 1 IN V EN TOR.

Oct. 3l, 1950 F. H. KLUG 2,527,937

HOT-AIR FURNACE Filed Aug. l0, 1948 2 Sheets-Sheet 2 INVENTOR.

Patented Oct. 31, 1950 OFFICE.. l

'HOT-AIR FURNACE Ferdinand H. Klug, BentonHarlior,V Mich.

Application August 10, 1948, SerialNo. 43,497'

This invention relates to improvements .in hot air. furnace. y

The principal objects of. this invention are:

First, to provide a furnace for dcvJmesticuse having increased eiciencyand rapid heat transfer characteristics.

Second, to provide a furnace having a lire tube heat exchanger whichiseasily cleaned so that the furnace may be maintained at peak operat- Iing efficiency without tearing down the furnace-` or.V employingspecialized Workmen.

Third, to provide a furnace with a horizontal re tube heat exchangerwhich is easily assembled as a unit on the remainder of thel furnace andwhich employs the principle of counterflow of the hot gasesv and the airbeing heated. f

Fourth, to. provide a furnace with a refractory.

combustion chamber which functions to store heat for hold-over heatingbetween operating periods of the burner and which at thesame time` doesnot materially obstruct the rapid passageofheat from the burnerk to theheat exchange surface.

Fifth, to provide a furnace having a divided 'i path of flow for the airbeingheated whereby part of the air is heated directly from the walls ofthe re chamber and part of the air is heated from a' re tube heatexchanger.

Other objects and advantages relating to details of my furnace will beapparent from a consideration of the following description andattacheddrawings. The inventionY isV further pointed out in the claims.

The drawings, of which thereare two sheetsy illustrate two forms of myfurnace.

Fig. 1 is aside elevational view, partially broken away in verticallongitudinal cross sec-- tion, of a rst form of my furnace.

Fig. 2 is a transverse vertical cross sectionalview taken along theplane of the linev 2-.2 of

Fig. 6 isy an enlarged` detailedfcross sectional:

. f 2 view taken along the plane ofthe line {if-6. in

Fig. 7 is a verticallongitudinal cross .sectional view through a secondform ofY my furnace.v

`My. furnace. consists generally of an upstanding rectangular fire'chamber l havingthe horizontally extending rectangularheat exchanger 2rextending from the upper yportion of the rear wall' thereof. bustionchamber 3 consisting of perforated `lire brick:l lor.` other refractorymaterial. A burner such as the gun type` oil burner 4 has its moutharranged through the front wall of the fire chamber and` combustionchamber to produce a llame within the combustion chamber. If desired, agasburnercan be substituted for the oil burner 4; The'fire. chamber Iland heat exchanger 2 are enclosed in aV suitable generally rectangularcasing 5:, .the walls of which are spaced from all walls of the lirechamber and heat exchanger excepting the' rear wall4 of the heatexchanger. The casing 5 andi heat exchangerZ dene a plenum chamber 6 inthe rear of the furnace and a cold airlreturn ductl is 'connected'through thefblower; 8rt'oV dischargev cold air into the plenum cham-lber... A..hot air outletV and stack collar 9 is providedonrth'estop ofthe casing just over the junction between the heat exchanger and thefire chamber.;

More specifically; the lire chamber lY com'- pris'es a sheet.' ofrelativelyheavy gauge sheet" I steel folded into rectangular shape andwelded as at. I wirr Fig. '31 The-front wall of the firechamberi's'provi'ded with an observation and clean-out noted'thatthecasing 5 is spaced from the front and side walls of the re chamber l.

v The heat. exchanger 2 consists of a front platev l "l land. rearpla-tell which are connected in spaced parallel relationship-by fourlongitudinally extending. angle irons I8.

Thef lire. chamber l encloses a com- The plates I6 and I1... denaaplurality of aligned apertures in which the.V ends'of the rertubes I9are secured. Asis most clearly shownY in Fig. .el the iretubes aresealed to-the plates' t6- and I1' by upsetting the ends of Ltheftubestof'orm'-theannular beads 20 which aref: sealed against theinside surfacesV of thepl'atesff: .'I'heeentlslY of! the,Vv tubesoutside of .the plates; are?.

' front plate IE of the heat exchanger.

then spun or swaged over the edges of the apertures as at 2I.

The flange I5 around the opening I4 in the fire chamber is providedwitha series of studs 22 which are welded to the fire chamber and projectrearwardly through holes provided therefor in the The periphery of theplate I6 is rearwardly oifset as at 23 so that a sealing compound 24 canbe positioned around the joint between the fire chamber and the heatexchanger. Nuts 25 clamp the heat exchanger to the re chamber.

After the front plate I6 has been bolted to the re chamber a rectangularsleeve 26 is slid over the angle irons I8 to enclose the re tubes I9 andcomplete the heat exchanger. The rear end of the heat exchanger issupported from the floor by a pair of posts 21. It will be noted thatthe sleeve 26 extends rearwardly beyond the rear plate I'I of the heatexchanger and beyond the rear Wall of the casing 5 (see Fig. 4).

`In order to separate the plenum chamber 6' from the upper portion ofthe casing 5, the lower side edges of the sleeve 26 are provided withbaille plates 28 which extend laterally to the side walls of the casing5. The forward ends of -the baille plates 28, adjacent to the rear wallof the nre chamber I, are provided with depending vertical baflles 29which support the vertically adjustable damper plates 30 for regulatingthe opening between the plenum 6 and the forward portion of the casing 5around the re chamber.

The rear end of the heat exchanger sleeve 26, which projects from therear of the casing, is secured by the folded lapped joint 3| (see Fig.4) to a rectangular smoke box 32. The smoke box is provided with acollar for attachment to the smoke pipe 33 and is further provided witha clean-out door 34 positioned at the bottom of wa-rdly through the coldair duct 'I by the blower 8 will be forced into the plenum chamber 6from where part of the air can pass forwardly through the openings 35underneath the damper plates 3U to around the sides of the re chamber I.Here the air will be heated and forced upwardly through the stack collar9. The rest of the air entering the plenum chamber will be forcedthrough an opening 38 formed at the rear of the bottom wall of thesleeve 26. From the rear of vthe heat ex-` changer the a-ir is forcedupwardly and forwardly opposite to the direction of the flow of the hotgases through the lire tubes, and isdischarged from the heat exchangerthrough the upper opening 3l adjacent to the stack collar 9. Thus partofthe air will be heated by the relatively hot walls of Vtheiire chamberwhile the remaining portion ofthe air will be heated by the relativelycooler `iretubes I5. The proportion of air passing over the two possibleroutes may be varied by adjusting the damper plates 38. Attention isinvited to the fact that the inspection door I3 is positioneddirectly infront of the fire tubes I9 so that it is a simple matter for thehouseholder to push a long handle brush directly through each offthe nre"tubes to force any soot which may have 4 collected therein into thesmoke box 32. The soot will fall to the bottom of the smoke box where itis easily removed through the clean-out door 34. It is thus easy to keepthe furnace in clean efficient operating condition.

In the modified form of the furnace illustrated in Fig. 7, the firechamber I, combustion chamber 3, and burner 4 are the same as in thefirst form of the furnace. The heat exchanger 2A is different from thefirst form of heat exchanger in that it is provided with an intermediatepartition plate 38 which divides the heat exchanger into two sections.The rear section of the heat exchanger is provided with an inlet collar39 to which the cold air duct 'IA is connected. In this case the duct'IA extends downwardly through the top wall of the casing 5A. The bottomwall of the sleeve 26A defines an opening 40, opening into the rearportion of the plenum chamber 6A. The plenum chamber is also dividedinto front and rear sections'by the partition plate 4I and the blower 8is positioned in the rear section of the plenum chamber to dischargethrough the partition plate 4I into'the forward section of the plenumchamber. From the forward section of the plenum chamber, air can passeither forwardly around 'the're chamber as in the first form of thefurnace,l or upwardly through an inlet opening 36A' inthe' bottom of theheat ex-fl I have thus described two highly practical forms of myfurnace which are very efficient inI operation and which materiallyreduce vthe temperature of the exhaust gases escaping up the chimney dueto more complete transfer of heat from the gases to the air beingheated. The elements of the furnaceare easily fabricated and assembledand the'furnace is Very easy to keep clean.

Having thus described my invention what I claim as new and desire tosecure by Letters Patent is:

1. A furnace'comprising a generally rectangular casing having a hot airoutlet inthe top thereof, walls forming an upstanding rectangular sheetmetal re chamber positioned in the front of said casing and spaced fromthe walls thereof,

the rear wall of said rire chamber defining an Y opening in the'upper`portion thereof, a heat ex changer comprising Afront and rear plateswith a plurality of fire tubes supported therebetween and extendingtherethrough, the front plate of said heat exchanger being secured tothe rear wall of saidre chamber and over said opening,y

the rear plate of said heat Vexchanger forming a and the sides of saidcasing and cooperating with' the bottom of said sleeve to form the topof a plenum chamber in the bottom of said casing,` adjustable damperplates positioned between the sides of said casing and the rear wall ofsaid Ifire chamber and extendingupwardly tosaid baille plates andarranged' to control the ilo'w offair inlet opening from said plenumchamber in the` rear portion of its lower wall and an outlet opening towithin the top of said casing in the forward portion of its top wall,means forming a combustion chamber of perforated refractory materialpositioned in said re chamber and spaced from the walls thereof, and aburner provided with a tube for projecting a name into said combustionchamber.

2. A furnace comprising a casing having a hot air outlet in the topthereof, walls forming an upstanding sheet metal re chamber positionedin the front of said casing and spaced from the Walls thereof, the rearwall of said fire chamber defining an opening in the upper portionthereof, a heat exchanger comprising front and rear plates with aplurality of re tubes supported therebetween and extending therethrough,the front plate of said heat exchanger being secured to the rear wall ofsaid re chamber and over said opening, the rear plate of said heatexchanger forming a portion of the rear wall of said casing,longitudinal bars connecting the corners of said plates, a sleevepositioned around said bars and enclosing said heat exchanger, baffleplates extending between the sides of said sleeve and the sides of saidcasing and cooperating with the bottom of said sleeve to form the top ofa plenum chamber in the bottom of said casing, damper plates positionedbetween the sides of said casing and the rear wall of Said fire chamberand extending upwardly to said bale plates and arranged to control thefiow of air from said plenum chamber to the space surrounding said firechamber, a smoke box secured to the rear end of said sleeve and having acleanout door positioned in the lower portion of said box, means fordelivering air to said plenum chamber, said sleeve defining an inletopening from said plenum chamber in its lower wall and an outlet openingto within the top of said casing in the forward portion of its top wall,means forming a combustion chamber of perforated refractory materialpositioned in said fire chamber and spaced from the walls thereof, and aburner arranged to provide a flame in said combustion chamber.

3. A furnace comprising a generally rectangular casing having a hot airoutlet in the upper portion thereof, walls forming an upstanding sheetmetal fire chamber positioned in the front of said casing and spacedfrom the walls thereof, the rear wall of said re chamber defining anopening in the upper portion thereof, a heat exchanger comprising frontand rear plates with a plurality of fire tubes extending therebetweenthe front plate of said heat exchanger being secured to the rear wall ofsaid fire chamber and over said opening, the rear plate of said heatexchanger forming a portion of the rear wall of said casing,longitudinal bars connecting the corners of said plates, a rectangularsleeve positioned around said bars and enclosing said heat exchanger,baiile plates extending between the sides of said sleeve and the sidesof said casing and cooperating with the bottom of said sleeve to formthe top of a plenum chamber in the bottom of said casing, damper platespositioned between the sides of said casing and the rear wall of saidfire chamber below said baffle plates and arranged to control the flowof air from said plenum chamber to the space surrounding said firechamber, a smoke box secured to the rear end of said heat exchanger andhaving a cleanout door positioned in the lower portion of said box,means for delivering air to said plenum chamber,

said sleeve defining an inlet opening from saidv plenum chamber in itslower wall and an outlet opening to within the top of said casing in itstop wall forwardly of said inlet opening, and a burner for developing aflame in said nre chamber.

4. A furnace comprising a casing having a hot air outlet in the upperportion thereof, walls forming an upstanding sheet metal re chamberpositioned in the front of said casing and spaced from the wallsthereof, the rear wall of said fire chamber defining an opening in theupper portion thereof, a heat exchanger comprising front and rear plateswith a plurality of horizontal fire tubes extending therebetween andopening therethrough, the front plate of said heat exchanger beingsecured to the rear wall of said re chamber and over said opening, arectangular sleeve enclosing said heat exchanger, baflle platesextending between the sides of said sleeve and the sides of said casingand cooperating with the bottom of said sleeve to form thetop yof aplenum chamber in the bottom of said casing, means for delivering air tosaid plenum chamber, said sleeve defining an inlet opening from Asaidplenum chamber in its lower wall and an outlet opening to within the topof said casing in its top wall forwardly of said inlet opening, and aburner for developing a flame in said fire chamber.

5. A furnace comprising a casing having a hot air outlet in the topthereof, walls forming an upstanding sheet metal fire chamber positionedv in the front of said casing and spaced from the walls thereof, `a heatexchanger in said casing comprising a plurality of' re tubes secured attheir front to the rear wall of said re chamber and communicating withsaid flre chamber, a sleeve positioned around and enclosing said heatexchanger, baffle plates extending between the sides of said sleeve andthe sides of said casing and cooperating with the bottom of said sleeveto form the top of a plenum chamber in the bottom of said casing, meansfor delivering air to said plenum chamber, said sleeve defining an inletopening from said plenum chamber in the rear portion of its lower walland an outlet opening to within the top of said casing in the forwardportion of its top wall, and a burner for developing a name in said firechamber.

FERDINAND H. KLUG.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS l Mallory Feb. 13, 1940

